There exists a great need for a single sensor capable of effectively performing both tactile and proximity sensing. In the sensor field, numerous types of tactile sensors and numerous types of proximity sensors have been proposed. However, in order to provide proximity and tactile sensing, one or more sensors of each type must be provided, resulting in undue complexity and cost. The art has not yet provided tactile and proximity sensing within a single sensor.
An example of a tactile sensor is disclosed in U.S. Pat. No. 4,588,348 to Beni, et al. This patent discloses a tactile sensor array and clearly states that it cannot perform proximity sensing (Col. 7, lines 35-37) and must be employed with a separate proximity sensor system to achieve proximity sensing. An example of a proximity sensor is disclosed in U.S. Pat. No. 4,541,771 also to Beni, et al. This patent also fails to provide both types of sensing. Beni '771 explicitly points to the fact that in order to provide both tactile and proximity sensing, a separate tactile sensing system must be employed (Col. 1, lines 50-54). It is significant to note that even while the inventors on each of these patents were the same and filed within only two months of each other, the inventors failed to combine both types of sensing in a single system as does the present invention.
In addition, many sensing devices can detect only magnetic objects. However, to be useful in a wide range of operating environments, there is a great need for sensors that can detect non-magnetic objects as well as magnetic objects.